Uni-Directional Catheter Overview
Many different medical treatments are facilitated by the use of percutaneous catheterization devices and techniques. Percutaneous catheterization techniques generally involve introducing catheters as object devices, such as diagnostic or treatment devices, into the vasculature or other internal biological locations through delivery devices. As such, we refer to a device as a "delivery device" when it facilitates the placement of another device or treatment modality at a desired location. Similarly, we refer to a device as an "object device" when it is the device to be delivered through or by a delivery device.
Most catheterization treatments involve common vascular access techniques. Generally, an initial puncture is made in a desired initial access vessel by a needle. A guide wire is then inserted through the internal bore of the needle and out of the needle's end into the vessel lumen. Next the needle is withdrawn while the wire is held in place in the vessel. A dilator device is threaded over the wire and through the puncture site to increase the hole diameter to appropriate dimensions for delivery and object devices to be placed therethrough. The dilator is then removed over the wire, with the wire still in place in the vessel.
Next, a vascular access introducer sheath is threaded over the wire and into the vessel. The wire is removed and the introducer sheath is left in place as a delivery device to provide co-axial access into the vascular tree wherein catheters, guidewires, and other object devices can be placed therethrough for treatment. Radiopaque materials are generally provided on these object devices for X-Ray visualization during in-vivo placement.
"Catheters" are generally elongated devices with two elongate end portions. For known catheter designs, each elongate end portion is generally adapted for a specific function distinct from the other end portion, e.g., one end for introduction into a body and the other end for connection to another piece of medical equipment. Conduit lumens often extend between the elongate end portions.
Catheters can serve dual roles as delivery devices and as object devices. They are used as delivery devices when equipped with a conduit lumen to facilitate the delivery of a fluid or another device, and may also be object devices when the catheter's placement at a desired in-vivo location is facilitated by a separate delivery device. Multiple catheters may be arranged in a telescoping co-axial arrangement with several of those catheters performing dual delivery device/object device roles. Percutaneous methods for delivering a particular object device for remote in-vivo treatment often employ such a telescoping arrangement.
Catheters often comprise a first catheter end portion that is a "catheter distal end" for placement into a patient's body space or into another device lumen leading to such a body space. At least one end hole or side hole port is usually provided on the catheter distal end to allow communication between the internal catheter lumen and the distal body space that houses the distal end portion. The catheter distal end is usually adapted to be an object device in the sense that it may be delivered to a desired site through a conduit delivery device or over a rail delivery device. Thus, very flexible materials are chosen to track through the tortuosities of distal body spaces. The catheter distal end is also adapted to be a delivery device when a lumen is provided such that another device can be delivered therethrough. Thus, materials and other design features, such as distal tip shape, may be chosen to optimize support that the catheter distal end can give for the delivery of the object device therethrough.
The second catheter end portion is generally the "catheter proximal end" that is closest to the physician and is generally adapted to receive or couple with another device or to be manipulated by the physician. Luer adaptors or couplers are often provided on the catheter proximal end for interfacing with other devices. Object devices to be delivered through the catheter are received into a lumen at the proximal end portion, often being guided therein by a proximal coupler. A proximal luer fitting may also be provided to engage a syringe or other fluid delivery means. Proximal end portion materials are often chosen to accommodate relatively straight, larger bore vasculature of the proximal anatomy, wherein this section resides during in-vivo use. The special features particular to the catheter proximal end also combine to accommodate physician manipulation during handling and use.
Thus, catheters known in the art are designed for "uni-directional" use. Each of two catheter body end portions is designed to meet a specific and distinct proximal or distal need, and is thus generally not designed to be interchangeable with the other. However, patient dependent anomalies such as disease states or anatomy may require different designs of a particular catheter type. Since only uni-directional devices are available, such different design requirements are most usually met by making available multiple designs of the same type of catheter. An alternative of providing bi-directional delivery catheters having interchangeable ends for variable proximal or distal use has not heretofore been known. Examples of the uni-directional design of known catheters include dilators, distal delivery catheters such as microcatheters and infusion catheters, and proximal delivery devices such as introducer sheaths and cartridges.
Uni-Directional Dilators
Dilators are generally catheters used to dilate a hole initially made in a vessel to enlarge the hole's diameter and so allow for device access through the enlarged hole and into the internal lumen. Dilators have a tapering outer profile at a distal end. The dilator's proximal end is often adapted with a coupler for interfacing with other devices. Dilators are adapted so that the reduced profile tip enters the initial needle puncture hole with relative ease. Advancing the increasing diameter of the dilator's taper through the hole forces the tissue defining the hole to stretch or controllably tear in order to accommodate the larger bore regions of the dilator. Removing the dilator thereafter leaves an access hole into the artery of desired diameter.
One example of a dilator and related method of use in catheterization procedures is disclosed in U.S. Pat. No. 5,098,392 to Fleischhacker et al. Fleischacker et al. discloses a dilator and introducer sheath locking system made up of a dilator containing an elongated dilator cannula with a tapered distal end, a gripping clamp secured to its proximal end and a peel-away introducer sheath with a tapered distal end and a proximal end containing a splittable handle. The splittable handle interacts with the gripping clamp of the dilator to prevent undesired rearward migration of the dilator within the introducer sheath. The dilator has a tapered distal end and a luer fitting is attached to the proximal end for use in combination with other medical instruments and as a support during insertion of the introducer set. Every component of this system, including the dilator itself, is uni-directional.
Where large bore access sites are required, a series of dilators may be required to increase the bore in a step-wise manner. It is believed that gradual widening of the puncture site through gradual tapers and/or step-wise use of multiple dilators minimizes the trauma and tearing of tissue from the spreading action when compared to a more abrupt dilation. For a given taper pitch, ideally chosen for desirably minimized traumaticity, larger desired access holes require longer axial lengths of the dilator to be advanced beyond the puncture site. However, the available anatomy for the distal advancement of the dilator may be limited in a particular case, based upon patient dependent anomalies such as disease or tortuosity. Where distal advancement of the dilator is an issue, and where large diameter access hole is needed, multiple dilators of varying diameters may be required.
Uni-Directional Delivery Catheters
While known dilators are uni-directional catheters for widening an access hole to initiate percutaneous catheterization procedures, known delivery catheters are also uni-directional and are placed percutaneously through the access hole as object devices to facilitate the delivery of treatment devices or other modalities. Delivery catheters may be designed to deliver object devices or other treatments either in remote distal anatomy or in more proximal anatomy that is closer to the initial access site.
Delivery devices adapted to be used in distal anatomy are often delivered to a desired distal location as an object device over a rail or through another delivery device. Object devices or fluids can then be introduced into a proximal port and delivered distally via a lumen, then out of a distal port and into the distal site. A proximal coupler such as a funnel introducer and/or luer adaptor is generally provided on one end for interfacing with other devices.
The uni-directional nature of known delivery catheter designs, although desirably efficacious for particular categories of device uses, may require multiple designs of a single type of device in order to accommodate patient dependent performance requirements. For instance, a delivery catheter having a highly flexible distal end for superior trackability in distally tortuous anatomy may not have enough structural support to allow efficacious delivery of an object device therethrough for some treatments, such as when a guidewire extends beyond the delivery device and must push through a totally occluded vessel. Where the anatomy does not require the level of trackability for which the delivery catheter is designed, yet requires more support, it may be desirable for the distal portion of the delivery catheter to be more stiff and supportive. In fact, for certain sub-categories of uses, the desired performance of the distal end may require features closer to those provided on the proximal end. However, the proximal end can not be interchangeably adapted to become the distal end in a uni-directional design.
Other distal delivery catheter design features, e.g. tip shapes, may also be desirable for particular sub-categories of uses, but not for others. Thus, there are many reasons that multiple designs may be required of a given type of uni-directional delivery catheter.
One example of a uni-directional microcatheter for delivering fluids such as radiopaque agents, vaso-occlusive agents, or pharmacological agents is described in U.S. Pat. No. 4,739,768 to Engelson. Engelson describes a microcatheter having a relatively stiff proximal segment dimensioned to track a guide wire from an access site to a region adjacent the internal tissue. A fitting is attached to the proximal segment, such as a standard syringe fitting for use in connecting a syringe to the catheter for fluid injection. The distal portion of the device is relatively flexible and is dimensioned to be tracked co-axially over a guidewire rail along the tortuous path within soft tissue. A radiopaque band is located at the distal end as a marker for radiographically assisted positioning of the catheter in-vivo.
Another example of an infusion catheter with an elongate tubular body having proximal and distal ends and a lumen extending therebetween is disclosed in U.S. Pat. No. 5,336,205 to Zenzen et al. Zenzen discloses a flow-directed catheter made up of an elongate tubular body formed of relatively stiff tapered proximal segment, a relatively flexible and strong distal segment, and a transition section of relatively intermediate stiffness. The proximal segment uses a tapered proximal section for attachment to a proximal end fitting for adapting the catheter to a syringe. Blood flow directs the flexible distal segment to the target site.
Much like distal delivery devices, other delivery devices adapted for more proximal uses also have uni-directional designs optimized for a particular use. However, also like known delivery devices, sub-categories of uses have required that multiple introducer designs be available to make up for the relatively inflexible uni-directional designs. A desirable alternative of providing bi-directional introducer devices with variably interchangeable design features on opposite catheter ends has not heretofore been made available. Examples of uni-directional proximal delivery devices are access introducer sheaths or cannulas, and pre-loaded implant introducer cartridges.
One example of an introducer device for introducing object devices into body vessels is disclosed in U.S. Pat. No. 5,098,392 to Fleischhacker et al. (discussed above). Fleischhacker discloses a peel-away introducer sheath for use with a dilator. The introducer sheath has a tapered distal end and a proximal end containing a splittable handle which interacts with the gripping clamp of the dilator to prevent undesired rearward migration of the dilator within the introducer sheath. If a variation of the distal tip shapes or taper geometry or material flexibility were required for a sub-category of use for this sheath, a second sheath would be required imparting the desired feature or features on the uni-directional introducer sheath's distal end portion.
Introducer catheters for introducing object devices into other delivery devices have more pronounced limitations associated with known uni-directional designs. Particularly of interest are introducer devices configured as cartridges that house pre-loaded implantable devices. Such cartridges have been found to be particularly useful for introducing certain types of vaso-occlusive coils into distal delivery catheters, which provide for distal delivery of such coils to a desired vessel or aneurysm site for artificial occlusion. For certain vaso-occlusion coils having variable properties at opposite coil ends, varied distal/proximal orientations of the internally housed coils may be desired to optimize the features of the coil ends for occlusion of a chosen site. To allow for such variable coil orientations during delivery, multiple pre-loaded uni-directional cartridges may be required.
Vaso-Occlusion Coils & Uni-Directional Delivery Methods
Various types of vaso-occlusion coil devices and related methods are known, primarily including detachable coils and non-detachable coils. Known introducer devices and delivery techniques for these coils are uni-directional.
One type of vaso-occlusion coil apparatus is the detachable vaso-occlusion coil. This type of coil is generally detachably integrated at its proximal end with an elongate pusher and is delivered to a desired location for occlusion, by means of the pusher, through a delivery catheter which terminates at or near the entrance zone of the desired location. Once the coil is extended out of the delivery catheter and into the desired location, the coil is detached from the pusher and left as an implant. The detachment means may be mechanical, such as the type described in U.S. Pat. No. 5,250,071 to Palermo, or may be electrolytic, such as the type described in U.S. Pat. No. 5,122,136 to Guglielmi et al. Detachable coils of the type disclosed in these references are necessarily uni-directional since the pusher mechanism is integrated with the proximal side of the coil prior to insertion.
Other types of vaso-occlusion coils are not integrated with a pusher but are independent devices. Such coils are generally pre-packaged in pre-loaded introducer catheters as cartridges and discharged therefrom into a distal delivery catheter. Either a separate pusher forces the coil out the distal end of the cartridge or pressurized fluid hydraulically delivers the pre-loaded implant. Such coils can only be delivered in one direction because the known introducer cartridges within which they are pre-loaded are uni-directional.
One type of non-detachable vaso-occlusion coil assembly that is not integral with a pusher is disclosed in U.S. Pat. No. 5,382,260 for "Embolization Device and Apparatus Including an Introducer Cartridge and Method for Delivering the Same," to Dormandy, et al. (introduced infra). The Dormandy '260 patent discloses an introducer cartridge having a distal extremity with a tapered tip and a hub mounted on a proximal extremity. The cartridge is introduced into a coil delivery catheter in a catheter system as described earlier, and a stylet is used to push the embolization device out of the introducer cartridge into a passage in the coil delivery catheter. A guide wire is then used to push the coil through the coil delivery catheter until it advances beyond the tip thereof and into the desired site for occlusion.
Another non-detachable vaso-occlusion coil that is pre-loaded in an introducer cartridge for delivery is disclosed in U.S. Pat. No. 5,382,259 to Phelps et al. Phelps discloses a vaso-occlusion coil that may be continuous or segmented, onto which a fibrous, woven or braided, tubular covering or element is attached. Phelps further discloses that the coil devices may be supplied prepackaged in a sterile cannula which is adapted to engage the proximal end of a delivery catheter.
To deliver the Phelps et al. coil device, the distal end of a delivery catheter is placed adjacent to a desired occlusion site, and the coil-containing cannula is placed into engagement with the proximal end of the catheter. The coils are then transferred from the cannula lumen into the catheter lumen by exerting a force on the proximal end of the coil. A flexible pusher device then is used to push the coil through the delivery catheter and out its distal end to the desired site.
Phelps et al. also indicates that the vaso-occlusion coils as having varying first and second ends. For instance, a braid covering may be attached only at one end of the braid. Additionally, coils having complex shapes with secondary diameters are disclosed wherein opposite coil end portions may have different orientations when distally released from a compressed state within the cannula and delivery catheter lumens. For example, C-shaped coils, multiple loop coils, coils having both large and small secondary diameters, and "cloverleaf" configured coils are disclosed.
Another non-detachable vaso-occlusion coil that is pre-loaded in a uni-directional introducer cartridge for delivery is disclosed in U.S. Pat. No. 4,994,069 to Ritchart et al. Ritchart et al. discloses a coiled wire for use in small-vessel vaso-occlusion and having a convoluted space filling conformation when in a relaxed condition, a linear configuration when in a stretched condition, and a memory from the stretched to the relaxed condition when released from a delivery catheter into a vessel.
The preferred method of use disclosed in Ritchart et al. includes providing the vaso-occlusion wire in a prepackaged form in a sterile canula which is adapted to engage the proximal end of the delivery catheter. The canula is attached to the delivery catheter and the wire is transferred into the delivery catheter by a short wire, then advanced therethrough by a pusher. Various coil secondary configurations are described, wherein the coil shape is restrained within the pre-loaded canula and delivery catheter lumen prior to being discharged into a body space. The introducer cannula is not shown or described in detail.
Another example of an embolic coil that is pre-loaded in an introduction device as a cartridge is described in U.S. Pat. No. 5,382,260 to Dormandy et. al. The Dormandy '260 patent discloses a co-axial telescoping arrangement including a femoral artery sheath, a guiding catheter, and a coil delivery catheter. A C-shaped embolization device such as a coil is provided in an introducer cartridge made of clear transparent plastic such as a radiation sterilizable polycarbonate. A tubular member of the cartridge is bendable but relatively rigid so that it can be utilized as an introducer. A distal extremity of the cartridge is provided with a tapered tip and a hub is mounted on the proximal extremity, the hub also being formed of clear radiation sterilizable polycarbonate. The pre-loaded coil can thus be delivered only in one direction.
A pre-loaded tube for delivery of a vein-branch blocking member is also disclosed in U.S. Pat. No. 5,342,394 to Matsuno et al. Matsuno discloses an apparatus and method for blocking a vein branch comprising a vein-branch blocking member pushed out of a delivery tube with a push-out member and into the vein. The outer tube is bent and slidably receives an inner tube with a distal storing portion filled with a vein-branch blocking member. A push-out member pushes out the blocking member in the vein branch. The pre-loaded inner tube is flexible and has a proximal end that is fixed with a grip that is adapted to engage the proximal end of the outer tube in various embodiments. The distal shape of the outer tube is between 60 and 120 degrees and allows the inner tube to be easily inserted in the vein branch branching from the lateral wall of the vein. An embodiment discloses an articulation means for the distal bend, but no way to have a straight end if desired. The proximal end of the tube, however, is straight but is not adapted to be used distally nor is the distal shaped end adapted to straighten and be interchangeably used proximally.
Another pre-loaded cartridge/embolus supply system and method is disclosed in U.S. Pat. No. 5,133,731 to Butler et al. The Butler '731 patent discloses a magazine of cartridges pre-loaded with artificial emboli that are discharged therefrom into an embolus-delivery catheter coupled to a dispenser housing and inserted through a venotomy into a body space such as a blood vessel. The disclosed cartridges have an enlarged outlet head at the front end and a different enlarged inlet head at the rear end, each head abutting an opposite wall of the magazine. The emboli are pre-loaded at the factory in a central cartridge lumen so that it is ready to be discharged through the outlet head when it is later "hit" during use by a slug of fluid expelled from a fluid supply assembly provided.
A hydraulic embolus delivery system and method using pre-loaded cartridges is disclosed by Butler et al. in U.S. Pat. No. 5,167,624. The Butler '624 patent discloses a hydraulic system for delivering an embolus from a pre-loaded cartridge coupled to the lumen of a delivery catheter. A benefit of alleviating the need for multiple pushers is described in the patent. The cartridge described in the Butler '624 patent has a passageway containing the pre-loaded coil in a stretched state, an inlet end to receive an injection stream of pressurized fluid from a source, and an outlet end through which the coil is discharged by way of the force imparted on the coil from the fluid injection. An alternative embodiment is disclosed having an inlet fitting at one end and an outlet mouth of the tubing at the other end for connecting to an introducer catheter. The fittings disclosed are of standard size and shape so that they mate easily with other attachment fittings.
A pre-loaded vaso-occlusion coil/introducer apparatus cartridge is also disclosed in pending U.S. patent application Ser. No. 08/413,970 for "Liquid Coils With Secondary Shape", filed Mar. 30, 1995. That document describes an occlusive implant having a pre-formed distal end and an extremely flexible proximal end. The coil is pre-loaded in an occlusive device cartridge or introducer. A sidearm adaptor fluidly couples the distal end of the cartridge to the proximal end of a delivery catheter. A syringe provides fluid flow to push the coil out of the cartridge, through the delivery catheter, and then out into the desired vessel site for occlusion. The pre-formed distal coil end has a greater flow resistance than the proximal portion of the coil such that the proximal coil portion desirably piles against the distal coil portion in a ball-like mass and engages a vessel wall for occlusion.
The cartridge includes a hub for receiving the discharge end of a syringe and a flexible elongated tubular member for discharging the occlusive device that is pre-packaged therein out of the tubular member and into the delivery catheter. The tubular member has a proximal end secured to a hub recess and a distal end adapted for being releasably secured within an inlet of the delivery catheter sidearm.
Various designs of vaso-occlusive coils are disclosed in U.S. Design patent application Ser. No. 29/037,001, filed Mar. 31, 1995 by Mariant et al. Several of these designs have differing secondary shapes at the opposite ends, for example wherein terminal ends of large loops of secondary helix shapes have different geometries due to the ends' orientation in relation to the handedness of the helix. As such, the space filling mechanisms may vary if one were to re-orient the direction that the shaped coils take when released from a stretched, confined state within an introducer and delivery tube lumen and into a less confined soft tissue space. However, when such coils are pre-loaded into known delivery cartridges their direction can not be re-oriented to vary the desired distal and proximal space filling geometries when released from a restraining delivery sheath. Existing uni-directional delivery cartridges don't allow for such re-orientation.
Thus, known delivery catheters such as microcatheters, infusion catheters, and introducer devices are uni-directional delivery devices having distinct and fixed proximal and distal ends. The particular design features in known delivery catheters, be them materials, dimensions, shapes, or orientation of housed implants, can be varied only by having multiple devices available that incorporate varying configurations. There is no known alternative to the uni-directional prior art in which the opposite ends of a catheter can be switched as distal and proximal ends in order to achieve varied catheter performance.
Most importantly, known vaso-occlusive coils can presently be delivered only uni-directionally because only uni-directional delivery catheters such as introducer cartridges are available. If a pre-loaded vaso-occlusion coil were desired to be delivered in a direction opposite its orientation within the cartridge with fixed distal and proximal ends, it would have to be removed and replaced in the desired orientation. Another solution to the problem would be to provide two coils in two uni-directional cartridges, one in each orientation--in other words to provide two devices, each having the coil pre-loaded in a cartridge in one of the two directions.
None of the references cited above provide a bi-directional catheter design that has two opposite ends that are adapted to interchangeably function as the catheter distal and proximal ends during use.
Nor do the references cited above provide a bi-directional catheter that is adapted for use as a single dilator device where both ends are adapted to be used for step-wise dilation of initial needle puncture sites in tissues to achieve relatively large-bore access diameters.
Nor do the references cited above provide a single bi-directional catheter that can facilitate the bi-directional delivery of implantable devices such as embolic coils that are pre-loaded in the catheter as a cartridge assembly.
The device features and related methods of the current invention provide solutions to these problems and more.